Automatic speed limiting device for hydraulic turbine rotors



Sept. 10,1946. P. w; SEEWER AUTOMATIC SPEED LIMITING DEVICE FORHYDRAULIC TURBINE ROTORS Filed Dec. 28; 1942 3 sheets sheet l 2 7 4 m U0 o I a?! v 2 fi v- 1. l m .6 3 HQ 1.

P ,VP. W.SEEWER 2,407,454

AUTOMATIC SPEED'LIMI'IING DEVICE FOR HYDRAULIC TURBINEROTORS Filed 0628, 1942 a Sheets-Sheet 2 Sept. 10, P. WER AUTOMATIC SPEED LIMITINGDEVICE FOR HYDRAULIC TURBINE ROTORS Fil ed Dec. 28, '1942 :sSheets-Sheet s Patented Sept. 1Q, 1946 AUTOMATIC SPEED LIMITING DEVICEFOR HYDRAULIC TURBINE ROTORS Paul Werner Seewer, Rugby, England,assignor to The English Electric, Company Limited, London, England, aBritish company Application December 28, 1942, Serial No. 470,396 InGreat Britain January 12, 1942 screams. (01. 253-7443) This inventionrelates to hydraulic turbines and has for its object to preventautomatically excessive runaway speeds. Although of general applicationit is of particular value when applied to turbines having swivellingpropeller type blades since as is Well known the problem of guardingagainst runaway of such turbines is particularly difficult.

The invention consists in speed-limiting means mounted on the turbinerotor and adapted, if a predetermined speed be exceeded, to project intothe stream and limit the speed of the rotor by exerting a braking torquethereon or by diverting or otherwise disturbing the water on its way tothe driving blades or by having a combination of these effects.

Preferably, the device according to the invention consists of aspeed-limiting unit in the form of a ring fastened tothe hub of theturbine rotor adjacent to and preferably above the turbine blades.Hinged or slidably mounted on or within this ring are braking ordeflecting vanes or like members normally retained against the action ofcentrifugal force and held out of the stream. When a certain speed isexceeded centrifugal force causes these members to project into thestream.

One form of the invention is .illustrated by Figures 1-4 and Figures 6and '7 ofthe accompanying drawings, of which Figure 1 is the left handhalf of a vertical cross-section through a complete hydraulic turbine ofthe swivelling propeller bladed type incorporating the invention; Figure2 is an enlargement of apart of the upper end of the turbine shown inFigure 1; Figure 3 is an enlargement of the pivoted braking vane shownin Figure 1; Figure 4 is a perspective view-showing the swivellingblades and a ring of braking vanes of part of the rotor of the turbineshown in Figure 1, the vanes projecting in the fully operative position;Figur 5 is a view corresponding to Figure 3 of a slightly modified formofv braking vane; and, Figures 6 and '7 are inclined views of a detailof Figure 2, but to a larger scale than Figure 2.

' In Fig. 1 the turbine is of conventional swivelling propeller bladedtype. The stator includes the enveloping turbine casing I from which theincoming water flows through the spaces between the pivoted shutters 2on its way to the rotor blades. The shutters are operated in the usualmanner by the lever and link mechanism indicated at 3 under theautomatic control of the turbine speed governor. The rotor comprises thea 2 vertical shaft 4 terminating in the hollow hub 5 carrying theswivelling blades 6.

Secured to the hub immediately above the blades 6 is the ring 1incorporating the automatic speed-limiting device according to theinvention. Within thi ring are mounted a number of braking vanes 8 eachof which is hinged as shown in Figs. 1 and 3 about a hinge pin 9 ,withits axis in a plane transverse to the rotor axis. Normally each of thevanes 8 is retained in the position shown in full lines so as to beexactly flushwith the curved circumferential surface of the ring 1 whichis a smooth continuation of the surface of the hub 5. vWhen under theaction of centrifugal force these vanes turn about their pivot pins 9the water vpressureas soon as the tips of the vane emerge-assists thevanes to fly out. In their outer position, the vanes 8 create adisturbing action on the incoming stream therebyreducing the drivingtorque exerted by the water on the turbine driving blades while at thesame time these vanes 8 can exercise a powerful braking torque on therotor by reason of their having to act against the incoming waterstream.

Although the device is efiective if the vanes 8 be parallel to the rotoraxis, the drawings show the axe of the hing pins 9 in planes which,although transverse to the rotor axis, are not horizontal but inclinedat an angle other than 90 to the rotor axis whereby the vanes 8, whenthey swing out, are not parallel to but are inclined to the rotor axisoppositely to the direction of the blades 6, as shown in Fig. 4, theirsurfaces thus having a more marked tendency to divert the incoming wateron its way to the driving blades 6. It will beappreciated, however, thatth axes of the hinge pins could be either horizontal or vertical and thesurfaces of the vanes either vertical or specially shaped to divert thewater.

Hinged vanes 8 are counter-balanced by portions such as in Fig. 3 toreduce the effect of centrifugal force, thereby allowing of the use ofweaker retaining means.

The vanes are provided with means normally retaining them flush with thering 1 until a certain centrifugal force and hence a certain speed isexceeded. These retaining means may be springs; alternatively they maybe breaking links which are snapped by the action of centrifugal force,or they may be a combination of springs and breaking links as shown inFigs. 1 and 2.

As shown in Figs. 1, 2 and 3 each vane 8 is connected by a flexiblecable l9-e. g. a steel wire ropepassing over an adjacent pulley ll onthe 3 rotor and vertically along a groove formed between the verticalshaft 4 and the usual protective sleeve l2 thereon (see Fig. 1) to theretaining means at the upper end of the shaft shown in the enlarged viewFig. 2. The upper end of the cable NJ is coiled around and anchored tothe drum l3 mounted on one of a number of bearings 2! carried by therotor. Turning with the drum I3 is another drum l4 while coiled aroundand anchored to the latter is another cable l5 directly attached to alink rod [6, the upper end l6a of which is of such reduced cross sectionas to snap when the desired pull is applied to the link which thusserves as a breaking link for releasing the associated vane 8 under theac-.

tion of a predetermined centrifugal force. In the arrangement shown thedrum I4 is of smaller diameter than the drum l3 so that the combinationforms a reducing arrangement whereby the movement of the broken link rodl6-when the associated vane flies out -is less than the movement of thecable Ill, but it will be understood that these drums could, if desired,be both of the same diameter or that the cable 10 could be directlyconnected to the link rod IS.

The link rod l6 slides through a guide sleeve 57 carried by the rotorand carries towards its upper end a collar [8. Surrounding the sleeve 51and the collar it between the flanges thereon is the coiled compressionspring I9 which is a comparatively light spring exerting on the cable l0only sufficient force to retain the associated Vane at a comparativelylow speed of the rotor.

The described retaining devices-one for each of the vanes 8are arrangedin a ring around the shaft and all are normally held up by theengagement of the upper end of each link rod IS with a latchZil' whichcan be released in known manner by the ordinarily provided overspeedtrip device. The well-known form of operating member for thisdevicecomprising the tappet pin 22 which, under the action ofcentrifugal force, can slide (against the action of the spring 23)radially outwards in the sleeve portion 24a forming part of the annularstructure 24 secured to and carried around by the shaft 4--can be seenin Figs. 2 and 6. The tappet 22, when it moves out, engages and movesthe operating lever 21 of the Well-known complementary part of the tripdevice attached to a fixed portion of the turbine casing, which partsets in motion valve means to cut off the supply of water to the rotorblades of the turbine, as already mentioned. The upper end of the saidoperating lever 21 which can be seen at 26 in Figures 2, 6 and 7 is thenin a position to engage the end of each latch 29 as they are moved insuccession past the lever 27 by the rotation of the shaft. Each latch isshown as being movable clear of the underside of the head of link rodpart ltd by turning about the vertical pivot pin secured on and carriedaround with the said annular structure 24, and will be so moved by theengagement with the end 26 of lever 21.

Figure 6 shows the tappet 22 in its normal position when it is justpassing the lever 21, while Figure '7 shows one of the latches 20 justpassing the upper part 26 of the lever 21; the chain lines in Figure 7show the position of part 26 when the tappet 22, in response toexcessive overspeed, has engaged lever 21, in which position part 26 canengage and move latch 29 as the turbine rotor rotates.

On a predetermined speed being exceeded, the latch device 20 is releasedby the overspeed trip 4 device, thus releasing the link rod 16. At thisspeed the centrifugal force acting on the vane 8 causes a pull on theupper cable is which while insufiicient to snap the reduced portion Iliaof the breaking link 16 is more than suflioient to overcome the upwardforc of the spring 19. Accordingly on the release of the latch device,all the vanes fly out substantially simultaneously under the action ofcentrifugal force aided by the action of the water once the vanes havestarted to move. In the unlikely event of any latches 20 not releasing,the individual breaking links l6 will snap under the action of thecentrifugal force at a slightl higher speed and so allow each vane tofly out. When the turbine rotor has subsequently been broughtsubstantially to a standstill, the springs H can pull up the cables l5and Ill to their normal position. and. withdraw the vanes into the ring1.

Operation of the speed limiting device can be seen since the latch 28visible and downward movement of the link rods !5 can be observed.

To facilitate this observation, markings la may be provided on the shaftadjacent to the flange oi" the collar 58 which moves down with the link16. Failure of any one of the retaining devices-womprising thecombination or" breaking link l6 and spring i9-to retain or withdraw itsassociated vane 8 can also be seen. In the unlikely event of breakage ofany one of the cables [0 or E5, the associated spring is will force thefree upper end of the link rod it above its normal position and thisagain can be seen. The retaining means, being outside the water, arereadily available for adjustment 'or replacement of the springs l9 andfor replacement of the breaking links it after snapping.

A modification is shown in Fig. 5 which is a section through one vaneand an end View of another vane of a ring of retarding vanes 8 eachslidably mounted within the ring 7 but with its surface shaped fordiverting the incoming water, as can be seen from the said end View. Thesliding vane 8 (shown in its outer position by the chain lines) takesthe place of the pivoted vane B of Fig. 3 and is connected by theflexible cable Ii] to retaining means exactly as already described withreference to Figs. 2 and 3; it will be clear that this sliding vane willtend to move out into the stream under the action of centrifugal forcejust as does the hinged vane previously described.

What I claim as my invention and desire to secure by Letters Patent is:

1. In combination, a hydraulic turbine rotor, driving blades mounted onthe rotor, a ring of speed-limiting vanes mounted on the rotor and freeto move outwardly under the action of centrifugal force into the waterstream to limit the speed of the rotor, a flexible cord attached to eachof said vanes and extending along the rotor to an exposed position abovethe water stream, guide pulleys for said cords and means holding theends of said cords at the said position above the water stream to retainsaid speed-limiting vanes out of the water stream until centrifugalforce corresponding to a predetermined safe rotor overspeed is exceeded.

2. In combination, a hydraulic turbine rotor, driving blades mounted onthe rotor, a ring of speed-limiting vanes mounted on the rotor andmovable under the action of centrifugal force into the Water stream tolimit the speed of the rotor, operative connections between said vanesand an exposed position above the water stream,

links at that position holding the ends of said operative connections,said links being proportioned to snap under the action of centrifugalforce on the vanes (transmitted through the operative connections) at apredetermined excessive rotor speed, springs exerting on said operativeconnections a vane-retaining force but so proportioned as to be overcomeby centrifugal force at a comparatively low rotor speed, a latch deviceretaining each of said links (together with the said springs) andlatch-releasing means responsive to an excessive rotor speed below thatspeed at which the links are proportioned to break.

3. In combination, a hydraulic turbine rotor, driving blades mounted onthe rotor, speed-limiting vanes mounted on the rotor and movable underthe action of centrifugal forc into the water stream to limit the speedof the rotor and means retaining said vanes out of the Water stream,said retaining means having a weakened part proportioned to break whenthe force thereon due to a predetermined safe overspeed of the 10turbine is exceeded.

PAUL WERNER SEEWER.

